Lighting unit



1,640,448 1927' c. A. B. HALVORSON. JR

LIGHTING UNIT wg f8, 1925 Inventor CromweLL A.B. H aLvor-son Jr.

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, HLs Attorngy Patented Aug. 30, 1927.

UNITED STATES PATENT OFFICE.

CROMW ELL A. B. KALVORSON, JR., F LYNN, MASSACHUSETTS, ASSIGNOB TOGENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

LIGHTING unrr.

Application filed February 28, 1925. Serial No. 12,424.

My invention relates to lighting units of a type which is especiallyadapted for highway lighting, although it may be used for interiorlighting as Well. Y a It is quite common to find in the lighting artunits which are adapted to illuminate uniformly a circular area or zoneabout the axis of the unit. In some instances a paraboloidal reflector.is used for this purpose 1-) and a secondary conic reflector isinterposed at any suitable distance in the path of the beam whichintercepts and uniformly distributes the light in the zone. But as faras I am aware, in no instance has there been used in a li hting unit amain reflector of the ellipsoi al type With'an auxiliary re flectorlocated at or about the conjugate focal point and having a light sourcelocated at the principal focal point, the axes of both reflectors beingcoincident for uniformly or asymmetrically lighting the zone.

It is an object of my invention to provide a unit with such elements forthe purposes indicated.

Furthermore, it is an object to construct the auxiliary reflector in theform of a curved surface of revolution for producing the uniform type ofillumination in the zone about the axis of the unit and,to construct 0the auxiliary reflector as a warped'or curved surface unsymmetrical withrespect to the axis of the unit to produce the asymmetric type ofillumination of the zone. The means for accomplishing the resultsindicated in the foregoing are hereinafter more fully set forth andclaimed, reference being had to the accompanying drawing in which Fig. 1shows the unit of my invention in section and in elevation; Fig. 2 is aperspective reduced drawing showing the main and auxiliary reflectorsand the source of light in their relative positions; and Fig. 3 is abottom view of the elements shown in Fig. 2.

Referring more in detail to the drawing, it will be seen that the unithas a main reflector 2, which reflector is ellipsoidal in form. At orabout the main focal point F the unit has a light source 3, and at theconjugate focal point F it has an auxiliary reflector 4. Enclosing theunit appears the globe 5, on the upper end of which rests theellipsoidal reflector 2, the lower end being provided with a circularflange 6. This flange may be suitably secured to the upper rim of theglobe 5 by means of screws 7.

It will be understood that the socket for the light source 3 may besupported by any suitable frame work which may, if desired, be made torest on the upper side of the reflector 2, also the auxiliary reflectoror the target 4, as it is sometimes called, is provided with a threadedstem 8, thereby adapting the target to be screwed to any suitablesupporting element at the base of the unit. It will be understoodfurther that the auxiliary reflector surface may be of any suitableform. It may be curved, convex or concave; the curve may be parabolic,hyperbolic, elliptical or spherical; or it may be partly concave orconvex, depending upon the character of light distributed desired.

\Vith a lighting uiiit having the elements illustrated and described,the rays of light originating at the focal point F, for example, willfollow a-path indicated by the arrows and the nature of the distributionwill be determined by the configuration of the surface of the target, asvery clearly indicated in Fig. 3. With a device of this type, in orderto change the nature of the distribution of light it is necessary onlyto take out the target 4 and replace it with another target having theproper form of reflecting surface.

It will be seen that with a unit such as applicant has devised he isable to produce a much Wider zone of light about the axis of the unitthan by using, for example, some other conicoidal form of mainreflector. It

will also be seen that a much broader zone of 1 light is obtained with amuch smaller auxiliary reflector at the conjugate focal region; and thatthe intensity of the light in the zone may be varied as desired bymaking the auxiliary reflector asymmetric in form.

Another advantage in applicants construction is that by using anellipsoidal reflector the auxiliary reflector may be made muph smallerand, therefore, the shadow cas by the unit will be less rominent.

While I have shown and described my invention in a specific and concreteform, it will be understood I do not Wish to be so limited, inasmuch asvariation and modification of my invention will readily suggestthemselves in view of the disclosure and may be roduced withoutdeparting from the spirlt of the invention or from the scope of theclaims herein.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. In a lighting unit, in combination, an ellipsoidal reflector, asource of light lo rated at the main focal point of the reflector, andan auxiliary asymmetrical reflector located between the main andconjugate points of the ellipsoidal reflector, the axes of the tworeflectors being parallel and whereby a converging beam of light isprojected toward the conjugate focal point of the cllipsoidal reflector.and intercepted by the aux iliary reflector and distributedasymmetrically in a zone about the axis of the unit.

In a lighting unit, in combination, an ellipsoidal reflector, a sourceof light located at the principal focal point, an auxiliary re flcctorlocated about the conjugate focal region of the elipsoidal reflector andhaving a surface generated about its longitudinal axis, the apex of theauxiliary reflector being located at a point between the two focalpoints of the ellipsoidal reflectors, whereby the beam of lightprojected toward the auxiliary reflector by the ellipsoidal reflector isdistributed asymmetrically in a zone about the axis of the unit.

3. In a lighting unit, in combination, a main ellipsoidal reflector, asource of light located at one focal region of the reflector and aconvex reflector covering the conjugate focal region of the mainreflector, the convex surface of the convex reflector being toward themain reflector and also being asymmetrical in configuration whereby aZone of light is produced about the axis of the unit having asymmetricdistribution.

In witness whereof. I have hereunto set my hand this 26th day ofFebruary, 1925.

CROMIVELL A. B. HALVORSON, J11

by Letters Patent of the 1. In a lighting unit, in combination, anellipsoidal reflector, a source of light located at the main focal pointof the reflector, and an auxiliary asymmetrical reflector locatcdbetween the main and conjugate points of the ellipsoidal reflector, theaxes of the two reflectors being parallel and whereby a converging beamof light is projected toward the conjugate focal point of theellipsoidal reflector. and intercepted by the auxiliary reflector anddistributed asy1nn1etri rally in a zone about the axis of the unit.

In a lighting unit, in combination, an ellipsoidal reflector, a sourceof light located at the principal focal point, an auxiliary reflectorlocated about the conjugate focal region of the elipsoidal reflector andhaving a surface generated about its longitudinal axis, the apex of theauxiliary reflector being United States, is,-

Patent No. 1,640,448.

CROMWELL A. B.

located at a point between the two focal points of the ellipsoidalreflectors, whereby the beam of light projected toward the auxiliaryreflector by the ellipsoidal reflector is distributed asymn'ietricallyin a zone about the axis of the unit.

In a lighting unit, in combination, a main ellipsoidal reflector, asource of light located at one focal region of the reflector and aconvex reflector covering the conjugate focal region of the mainreflector, the convex surface of the convex reflector being toward themain reflector and also being asymmetrical in configuration whereby azone of light is produced about the axis of the unit having asymmetricdistribution.

In witness whereof. I have hereunto set my hand this 26th day ofFebruary, 1925.

CROMWELL A. B. HALVORSON, J R.

Granted August 30, 1927, to HALVORSON, JR.

It is hereby certified that error appears in the printed specificationof the above numbered. atent requiring correction as follows: Page 2,lme 10, claim 1, for the word of read by; and that the said LettersPatent should be read with this correction therein that Ofiioe the samemay conform to the record of the case in the Patent Signed and sealedthis 11th day of October, A. n. 1927.

M. J. MOORE, Acting 00mmof Patents.

Certificate of Correction. Patent No. 1,640,448. Granted August 30,1927, to CROM WELL A. B. HALVORSON, Jn.

It is hereby certified that error appears in the printed specificationof the abovenumbered. atent requiring correction as follows: Page 2,line 10, claim 1, for the word of read by; and that the said LettersPatent should be read with this oorredzion therein that the same mayconform to the record of the case in the Patent signed and sealed this11th day of October, A. 1). 1927.

[mm] M. J. MOORE,

Acting Umnmim'our of Patents.

